diff --git a/src/allmydata/test/cli/test_backup.py b/src/allmydata/test/cli/test_backup.py
index de5911abd..5d39e2825 100644
--- a/src/allmydata/test/cli/test_backup.py
+++ b/src/allmydata/test/cli/test_backup.py
@@ -38,7 +38,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
 
     def test_backup(self):
         self.basedir = "cli/Backup/backup"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # is the backupdb available? If so, we test that a second backup does
         # not create new directories.
@@ -356,7 +356,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
             raise unittest.SkipTest("Symlinks are not supported by Python on this platform.")
 
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         source = os.path.join(self.basedir, "home")
         self.writeto("foo.txt", "foo")
@@ -387,7 +387,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
 
     def test_ignore_unreadable_file(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         source = os.path.join(self.basedir, "home")
         self.writeto("foo.txt", "foo")
@@ -421,7 +421,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
 
     def test_ignore_unreadable_directory(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         source = os.path.join(self.basedir, "home")
         os.mkdir(source)
@@ -457,7 +457,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
         # 'tahoe backup' should output a sensible error message when invoked
         # without an alias instead of a stack trace.
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         source = os.path.join(self.basedir, "file1")
         d = self.do_cli('backup', source, source)
         def _check((rc, out, err)):
@@ -471,7 +471,7 @@ class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
         # 'tahoe backup' should output a sensible error message when invoked
         # with a nonexistent alias.
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         source = os.path.join(self.basedir, "file1")
         d = self.do_cli("backup", source, "nonexistent:" + source)
         def _check((rc, out, err)):
diff --git a/src/allmydata/test/cli/test_check.py b/src/allmydata/test/cli/test_check.py
index 413360d3e..0eaf69099 100644
--- a/src/allmydata/test/cli/test_check.py
+++ b/src/allmydata/test/cli/test_check.py
@@ -358,7 +358,7 @@ class Check(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe check' should output a sensible error message if it needs to
         # find the default alias and can't
         self.basedir = "cli/Check/check_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("check")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -373,7 +373,7 @@ class Check(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe check' should output a sensible error message if it needs to
         # find an alias and can't.
         self.basedir = "cli/Check/check_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("check", "nonexistent:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -385,7 +385,7 @@ class Check(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_check_with_multiple_aliases(self):
         self.basedir = "cli/Check/check_with_multiple_aliases"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         self.uriList = []
         c0 = self.g.clients[0]
         d = c0.create_dirnode()
diff --git a/src/allmydata/test/cli/test_cli.py b/src/allmydata/test/cli/test_cli.py
index 8974f8c09..47dff8171 100644
--- a/src/allmydata/test/cli/test_cli.py
+++ b/src/allmydata/test/cli/test_cli.py
@@ -714,7 +714,7 @@ class Ln(GridTestMixin, CLITestMixin, unittest.TestCase):
         # exist, 'tahoe ln' should output a useful error message and not
         # a stack trace
         self.basedir = "cli/Ln/ln_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("ln", "from", "to")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -734,7 +734,7 @@ class Ln(GridTestMixin, CLITestMixin, unittest.TestCase):
         # If invoked with aliases that don't exist, 'tahoe ln' should
         # output a useful error message and not a stack trace.
         self.basedir = "cli/Ln/ln_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("ln", "havasu:from", "havasu:to")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -845,7 +845,7 @@ class Errors(GridTestMixin, CLITestMixin, unittest.TestCase):
         # When the http connection breaks (such as when node.url is overwritten
         # by a confused user), a user friendly error message should be printed.
         self.basedir = "cli/Errors/test_broken_socket"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # Simulate a connection error
         def _socket_error(*args, **kwargs):
@@ -867,7 +867,7 @@ class Get(GridTestMixin, CLITestMixin, unittest.TestCase):
         # without an explicit alias and when the default 'tahoe' alias
         # hasn't been created yet.
         self.basedir = "cli/Get/get_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli('get', 'file')
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -880,7 +880,7 @@ class Get(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe get' should output a useful error message when invoked with
         # an explicit alias that doesn't exist.
         self.basedir = "cli/Get/get_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("get", "nonexistent:file")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -897,7 +897,7 @@ class Manifest(GridTestMixin, CLITestMixin, unittest.TestCase):
         # without an explicit alias when the default 'tahoe' alias is
         # missing.
         self.basedir = "cli/Manifest/manifest_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("manifest")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -910,7 +910,7 @@ class Manifest(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe manifest' should output a useful error message when invoked
         # with an explicit alias that doesn't exist.
         self.basedir = "cli/Manifest/manifest_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("manifest", "nonexistent:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -924,7 +924,7 @@ class Manifest(GridTestMixin, CLITestMixin, unittest.TestCase):
 class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_mkdir(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         d = self.do_cli("create-alias", "tahoe")
         d.addCallback(lambda res: self.do_cli("mkdir", "test"))
@@ -938,7 +938,7 @@ class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_mkdir_mutable_type(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("create-alias", "tahoe")
         def _check((rc, out, err), st):
             self.failUnlessReallyEqual(rc, 0)
@@ -967,7 +967,7 @@ class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_mkdir_mutable_type_unlinked(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("mkdir", "--format=SDMF")
         def _check((rc, out, err), st):
             self.failUnlessReallyEqual(rc, 0)
@@ -1003,7 +1003,7 @@ class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_mkdir_unicode(self):
         self.basedir = os.path.dirname(self.mktemp())
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         try:
             motorhead_arg = u"tahoe:Mot\u00F6rhead".encode(get_io_encoding())
@@ -1024,7 +1024,7 @@ class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
         # when invoked with an alias that doesn't exist, 'tahoe mkdir' should
         # output a sensible error message rather than a stack trace.
         self.basedir = "cli/Mkdir/mkdir_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("mkdir", "havasu:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1047,7 +1047,7 @@ class Unlink(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe unlink' should behave sensibly when invoked without an explicit
         # alias before the default 'tahoe' alias has been created.
         self.basedir = "cli/Unlink/%s_without_alias" % (self.command,)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli(self.command, "afile")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1063,7 +1063,7 @@ class Unlink(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe unlink' should behave sensibly when invoked with an explicit
         # alias that doesn't exist.
         self.basedir = "cli/Unlink/%s_with_nonexistent_alias" % (self.command,)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli(self.command, "nonexistent:afile")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1079,7 +1079,7 @@ class Unlink(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_unlink_without_path(self):
         # 'tahoe unlink' should give a sensible error message when invoked without a path.
         self.basedir = "cli/Unlink/%s_without_path" % (self.command,)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         self._create_test_file()
         d = self.do_cli("create-alias", "tahoe")
         d.addCallback(lambda ign: self.do_cli("put", self.datafile, "tahoe:test"))
@@ -1106,7 +1106,7 @@ class Rm(Unlink):
 class Stats(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_empty_directory(self):
         self.basedir = "cli/Stats/empty_directory"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         c0 = self.g.clients[0]
         self.fileurls = {}
         d = c0.create_dirnode()
@@ -1136,7 +1136,7 @@ class Stats(GridTestMixin, CLITestMixin, unittest.TestCase):
         # alias is created, 'tahoe stats' should output an informative error
         # message, not a stack trace.
         self.basedir = "cli/Stats/stats_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("stats")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1149,7 +1149,7 @@ class Stats(GridTestMixin, CLITestMixin, unittest.TestCase):
         # when invoked with an explicit alias that doesn't exist,
         # 'tahoe stats' should output a useful error message.
         self.basedir = "cli/Stats/stats_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("stats", "havasu:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1165,7 +1165,7 @@ class Webopen(GridTestMixin, CLITestMixin, unittest.TestCase):
         # should output an informative error message instead of a stack
         # trace.
         self.basedir = "cli/Webopen/webopen_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("webopen", "fake:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -1189,7 +1189,7 @@ class Webopen(GridTestMixin, CLITestMixin, unittest.TestCase):
             webbrowser.open = call_webbrowser_open
 
             self.basedir = "cli/Webopen/webopen"
-            self.set_up_grid()
+            self.set_up_grid(oneshare=True)
             d = self.do_cli("create-alias", "alias:")
             def _check_alias((rc, out, err)):
                 self.failUnlessReallyEqual(rc, 0, repr((rc, out, err)))
diff --git a/src/allmydata/test/cli/test_cp.py b/src/allmydata/test/cli/test_cp.py
index 937edd997..50b538d2f 100644
--- a/src/allmydata/test/cli/test_cp.py
+++ b/src/allmydata/test/cli/test_cp.py
@@ -32,7 +32,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
         self.skip_if_cannot_represent_filename(fn1)
 
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         DATA1 = "unicode file content"
         fileutil.write(fn1, DATA1)
@@ -76,7 +76,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
         # cp -r on a directory containing a dangling symlink shouldn't assert
         self.basedir = "cli/Cp/dangling_symlink_vs_recursion"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         dn = os.path.join(self.basedir, "dir")
         os.mkdir(dn)
         fn = os.path.join(dn, "Fakebandica")
@@ -90,7 +90,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_copy_using_filecap(self):
         self.basedir = "cli/Cp/test_copy_using_filecap"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         outdir = os.path.join(self.basedir, "outdir")
         os.mkdir(outdir)
         fn1 = os.path.join(self.basedir, "Metallica")
@@ -172,7 +172,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
         # when invoked with an alias or aliases that don't exist, 'tahoe cp'
         # should output a sensible error message rather than a stack trace.
         self.basedir = "cli/Cp/cp_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("cp", "fake:file1", "fake:file2")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -200,7 +200,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
         self.skip_if_cannot_represent_filename(fn1)
 
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         d = self.do_cli("create-alias", "tahoe")
         d.addCallback(lambda res: self.do_cli("mkdir", "tahoe:test/" + artonwall_arg))
@@ -224,7 +224,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_cp_replaces_mutable_file_contents(self):
         self.basedir = "cli/Cp/cp_replaces_mutable_file_contents"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # Write a test file, which we'll copy to the grid.
         test_txt_path = os.path.join(self.basedir, "test.txt")
@@ -447,7 +447,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe cp should print an error when asked to overwrite a
         # mutable file that it can't overwrite.
         self.basedir = "cli/Cp/overwrite_readonly_mutable_file"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # This is our initial file. We'll link its readcap into the
         # tahoe: alias.
@@ -574,7 +574,7 @@ class Cp(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_cp_verbose(self):
         self.basedir = "cli/Cp/cp_verbose"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # Write two test files, which we'll copy to the grid.
         test1_path = os.path.join(self.basedir, "test1")
@@ -606,7 +606,7 @@ starting copy, 2 files, 1 directories
         # https://tahoe-lafs.org/trac/tahoe-lafs/ticket/712
 
         self.basedir = "cli/Cp/cp_copies_dir"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         subdir = os.path.join(self.basedir, "foo")
         os.mkdir(subdir)
         test1_path = os.path.join(subdir, "test1")
@@ -640,7 +640,7 @@ starting copy, 2 files, 1 directories
         # a local directory without a specified file name.
         # https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2027
         self.basedir = "cli/Cp/cp_verbose"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         # Write a test file, which we'll copy to the grid.
         test1_path = os.path.join(self.basedir, "test1")
@@ -1008,7 +1008,7 @@ class CopyOut(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_cp_out(self):
         # test copying all sorts of things out of a tahoe filesystem
         self.basedir = "cli_cp/CopyOut/cp_out"
-        self.set_up_grid(num_servers=1)
+        self.set_up_grid(num_servers=1, oneshare=True)
 
         d = self.do_setup()
         d.addCallback(lambda ign: self.do_tests())
diff --git a/src/allmydata/test/cli/test_create_alias.py b/src/allmydata/test/cli/test_create_alias.py
index 181fadfc9..8d2efe29f 100644
--- a/src/allmydata/test/cli/test_create_alias.py
+++ b/src/allmydata/test/cli/test_create_alias.py
@@ -24,7 +24,7 @@ class CreateAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_create(self):
         self.basedir = "cli/CreateAlias/create"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         aliasfile = os.path.join(self.get_clientdir(), "private", "aliases")
 
         d = self.do_cli("create-alias", "tahoe")
@@ -148,7 +148,7 @@ class CreateAlias(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_create_unicode(self):
         self.basedir = "cli/CreateAlias/create_unicode"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         try:
             etudes_arg = u"\u00E9tudes".encode(get_io_encoding())
diff --git a/src/allmydata/test/cli/test_list.py b/src/allmydata/test/cli/test_list.py
index 644b6ee62..17b58a817 100644
--- a/src/allmydata/test/cli/test_list.py
+++ b/src/allmydata/test/cli/test_list.py
@@ -165,7 +165,7 @@ class List(GridTestMixin, CLITestMixin, unittest.TestCase):
         # doing just 'tahoe ls' without specifying an alias or first
         # doing 'tahoe create-alias tahoe' should fail gracefully.
         self.basedir = "cli/List/list_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("ls")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -178,7 +178,7 @@ class List(GridTestMixin, CLITestMixin, unittest.TestCase):
         # doing 'tahoe ls' while specifying an alias that doesn't already
         # exist should fail with an informative error message
         self.basedir = "cli/List/list_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("ls", "nonexistent:")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -245,7 +245,7 @@ class List(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_list_mdmf(self):
         # 'tahoe ls' should include MDMF files.
         self.basedir = "cli/List/list_mdmf"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self._create_directory_structure()
         d.addCallback(lambda ignored:
             self.do_cli("ls", self._dircap))
@@ -262,7 +262,7 @@ class List(GridTestMixin, CLITestMixin, unittest.TestCase):
         # 'tahoe ls' should include MDMF caps when invoked with MDMF
         # caps.
         self.basedir = "cli/List/list_mdmf_json"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self._create_directory_structure()
         d.addCallback(lambda ignored:
             self.do_cli("ls", "--json", self._dircap))
diff --git a/src/allmydata/test/cli/test_magic_folder.py b/src/allmydata/test/cli/test_magic_folder.py
index a70b8e4bc..71024ca0c 100644
--- a/src/allmydata/test/cli/test_magic_folder.py
+++ b/src/allmydata/test/cli/test_magic_folder.py
@@ -135,7 +135,7 @@ class MagicFolderCLITestMixin(CLITestMixin, GridTestMixin):
         return magicfolder
 
     def setup_alice_and_bob(self, alice_clock=reactor, bob_clock=reactor):
-        self.set_up_grid(num_clients=2)
+        self.set_up_grid(num_clients=2, oneshare=True)
 
         self.alice_magicfolder = None
         self.bob_magicfolder = None
@@ -188,7 +188,7 @@ class MagicFolderCLITestMixin(CLITestMixin, GridTestMixin):
 class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
     def test_create_and_then_invite_join(self):
         self.basedir = "cli/MagicFolder/create-and-then-invite-join"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         local_dir = os.path.join(self.basedir, "magic")
         abs_local_dir_u = abspath_expanduser_unicode(unicode(local_dir), long_path=False)
 
@@ -207,7 +207,7 @@ class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
 
     def test_create_error(self):
         self.basedir = "cli/MagicFolder/create-error"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         d = self.do_cli("magic-folder", "create", "m a g i c:", client_num=0)
         def _done((rc, stdout, stderr)):
@@ -218,7 +218,7 @@ class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
 
     def test_create_invite_join(self):
         self.basedir = "cli/MagicFolder/create-invite-join"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         local_dir = os.path.join(self.basedir, "magic")
         abs_local_dir_u = abspath_expanduser_unicode(unicode(local_dir), long_path=False)
 
@@ -262,7 +262,7 @@ class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
     def test_join_twice_failure(self):
         self.basedir = "cli/MagicFolder/create-join-twice-failure"
         os.makedirs(self.basedir)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         local_dir = os.path.join(self.basedir, "magic")
         abs_local_dir_u = abspath_expanduser_unicode(unicode(local_dir), long_path=False)
 
@@ -292,7 +292,7 @@ class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
     def test_join_leave_join(self):
         self.basedir = "cli/MagicFolder/create-join-leave-join"
         os.makedirs(self.basedir)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         local_dir = os.path.join(self.basedir, "magic")
         abs_local_dir_u = abspath_expanduser_unicode(unicode(local_dir), long_path=False)
 
@@ -323,7 +323,7 @@ class CreateMagicFolder(MagicFolderCLITestMixin, unittest.TestCase):
     def test_join_failures(self):
         self.basedir = "cli/MagicFolder/create-join-failures"
         os.makedirs(self.basedir)
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         local_dir = os.path.join(self.basedir, "magic")
         abs_local_dir_u = abspath_expanduser_unicode(unicode(local_dir), long_path=False)
 
diff --git a/src/allmydata/test/cli/test_mv.py b/src/allmydata/test/cli/test_mv.py
index 6b64af715..1c72d79b4 100644
--- a/src/allmydata/test/cli/test_mv.py
+++ b/src/allmydata/test/cli/test_mv.py
@@ -10,7 +10,7 @@ timeout = 480 # deep_check takes 360s on Zandr's linksys box, others take > 240s
 class Mv(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_mv_behavior(self):
         self.basedir = "cli/Mv/mv_behavior"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         fn1 = os.path.join(self.basedir, "file1")
         DATA1 = "Nuclear launch codes"
         fileutil.write(fn1, DATA1)
@@ -104,7 +104,7 @@ class Mv(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_mv_error_if_DELETE_fails(self):
         self.basedir = "cli/Mv/mv_error_if_DELETE_fails"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         fn1 = os.path.join(self.basedir, "file1")
         DATA1 = "Nuclear launch codes"
         fileutil.write(fn1, DATA1)
@@ -147,7 +147,7 @@ class Mv(GridTestMixin, CLITestMixin, unittest.TestCase):
         # creating the default 'tahoe' alias should fail with a useful
         # error message.
         self.basedir = "cli/Mv/mv_without_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("mv", "afile", "anotherfile")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -173,7 +173,7 @@ class Mv(GridTestMixin, CLITestMixin, unittest.TestCase):
         # doing 'tahoe mv' with an alias that doesn't exist should fail
         # with an informative error message.
         self.basedir = "cli/Mv/mv_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("mv", "fake:afile", "fake:anotherfile")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
diff --git a/src/allmydata/test/cli/test_put.py b/src/allmydata/test/cli/test_put.py
index f8d950aaa..1b3189f55 100644
--- a/src/allmydata/test/cli/test_put.py
+++ b/src/allmydata/test/cli/test_put.py
@@ -19,7 +19,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe get `echo DATA | tahoe put -`
         self.basedir = "cli/Put/unlinked_immutable_stdin"
         DATA = "data" * 100
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("put", stdin=DATA)
         def _uploaded(res):
             (rc, out, err) = res
@@ -45,7 +45,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe put /tmp/file.txt
         # tahoe put ~/file.txt
         self.basedir = "cli/Put/unlinked_immutable_from_file"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         rel_fn = os.path.join(self.basedir, "DATAFILE")
         abs_fn = unicode_to_argv(abspath_expanduser_unicode(unicode(rel_fn)))
@@ -75,7 +75,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe put file.txt DIRCAP:./uploaded.txt
         # tahoe put file.txt DIRCAP:./subdir/uploaded.txt
         self.basedir = "cli/Put/immutable_from_file"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         rel_fn = os.path.join(self.basedir, "DATAFILE")
         # we make the file small enough to fit in a LIT file, for speed
@@ -154,7 +154,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe get FILECAP, compare against DATA2
         # tahoe put file.txt FILECAP
         self.basedir = "cli/Put/mutable_unlinked"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         DATA = "data" * 100
         DATA2 = "two" * 100
@@ -200,7 +200,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # tahoe get uploaded.txt, compare against DATA2
 
         self.basedir = "cli/Put/mutable"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         DATA1 = "data" * 100
         fn1 = os.path.join(self.basedir, "DATA1")
@@ -259,7 +259,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_format(self):
         self.basedir = "cli/Put/format"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         data = "data" * 40000 # 160kB total, two segments
         fn1 = os.path.join(self.basedir, "data")
         fileutil.write(fn1, data)
@@ -326,7 +326,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_put_to_mdmf_cap(self):
         self.basedir = "cli/Put/put_to_mdmf_cap"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         data = "data" * 100000
         fn1 = os.path.join(self.basedir, "data")
         fileutil.write(fn1, data)
@@ -372,7 +372,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
 
     def test_put_to_sdmf_cap(self):
         self.basedir = "cli/Put/put_to_sdmf_cap"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         data = "data" * 100000
         fn1 = os.path.join(self.basedir, "data")
         fileutil.write(fn1, data)
@@ -410,7 +410,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         # when invoked with an alias that doesn't exist, 'tahoe put'
         # should output a useful error message, not a stack trace
         self.basedir = "cli/Put/put_with_nonexistent_alias"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
         d = self.do_cli("put", "somefile", "fake:afile")
         def _check((rc, out, err)):
             self.failUnlessReallyEqual(rc, 1)
@@ -430,7 +430,7 @@ class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
         self.skip_if_cannot_represent_filename(u"\u00E0 trier.txt")
 
         self.basedir = "cli/Put/immutable_from_file_unicode"
-        self.set_up_grid()
+        self.set_up_grid(oneshare=True)
 
         rel_fn = os.path.join(unicode(self.basedir), u"\u00E0 trier.txt")
         # we make the file small enough to fit in a LIT file, for speed